Functional electrical stimulation ergometer including automatic spasm control

ABSTRACT

This invention controls stimulation levels and cycling cadence on an FES ergometer to minimize or prevent the occurrence of spasm in spinal cord injured or other neurologically impaired patients.

FIELD OF THE INVENTION

The invention relates to functional electrical stimulation (FES) systemsfor rehabilitation of individuals suffering from neurological injuries.More particularly, the present invention relates to a device thatutilizes both mechanical and electrical stimulation of individual'smuscles.

BACKGROUND OF THE INVENTION

Spinal cord injured patients gain great benefit from riding on FESenabled ergometers. However, when a patient's limbs are set in motionand/or when stimulation is applied at the start of a session manypatients suffer from muscle spasms. This spasm often prevents thepatients from riding for several minutes until the spasms have subsided.This can cause time to be lost by both the patient andtherapist/care-giver and results in reducing the benefits that thepatient receives from the FES ergometer.

Current techniques to minimize spasm include:

1. Stretching the patient's legs prior to riding. The problem with thisapproach is that it is labor intensive and does not always achieve thedesired results.

2. Having the therapist observe the patient as stimulation is beingapplied and manually prevent the stimulation from increasing when thepatient is showing early signs of spasm. The problem with this approachis that it requires a well-trained therapist to be present when thepatient cycles. This is not always practical.

3. Setting the FES ergometer to increase the stimulation levels on thesubject very slowly so that the patient's muscles accommodate thestimulation. The problem with this solution is that a therapist needs tobe trained to know how to set-up the FES ergometer for a patient knownto have spasms. Another problem is that it takes longer for the patientto receive the maximum benefit of FES cycling because the stimulationramps up slowly. The patient may only occasionally suffer from spasm inwhich case it would be better to ramp up stimulation more quickly whenthe patient is not suffering from spasm.

BRIEF DESCRIPTION OF THE INVENTION

According to the invention, there is provided a functional electricalstimulation device having a left extremity support and a right extremitysupport, wherein both extremity supports are connected to a primarydrive motor that causes the extremity supports to move in a reciprocalmotion; the left extremity support is connected to a left extremitysupport servo motor and the right extremity support is connected to aright extremity support servo motor, wherein each of said right and leftextremity support servo motors causes its respective extremity supportto rotate about an axis. The device further has a control unit connectedto the left and right extremity support servo motors which controls theactuation of the left and right extremity support servo motors. Thecontrol unit may also include functional electrical stimulation leadsattached to skin adhesive electrodes which deliver electricalstimulation to a patient's muscles.

The device also includes an automatic spasm control system including amonitor which continuously monitors the torque required to rotate one orboth of the left and right extremity supports and a controllerconfigured to calculate a rate of change of said torque, and tocalculate a maximum electrical stimulation, a maximum stimulationramp-up rate, a maximum servo-motor speed and a maximum servo-motorramp-up rate.

According to further embodiments, the functional electrical stimulationsystem has two drive arms connecting the primary drive motor to each ofsaid left and right extremity supports, the drive arms optionally havingvarious attachment points for connecting to corresponding right and leftcranks at different attachment positions. According to furtherembodiments, the extremity supports are attached to the drive arms bythe corresponding left and right cranks.

According to further embodiments of the invention, the controller ofsaid automatic spasm control system is configured to identify a possibleonset of spasm when a monitored amount of torque or rate of change oftorque exceeds a predetermined value, and when a monitored amount oftorque or rate of change of torque exceeds said predetermined value, tocompare a current level of electrical stimulation to said calculatedmaximum stimulation and to compare a current crank speed to saidcalculated maximum crank speed and to send instructions to said controlunit connected to the left and right extremity support servo motors andto said functional electrical stimulation leads to reduce the amount ofelectrical stimulation and crank speed.

According to further embodiments of the invention, there is provided atherapeutic muscle exercise device having a cycling base configured toaccept a subject's upper or lower extremities and assist a subject inexercising the subject's muscles; the cycling base having a firstextremity support and a second extremity support, wherein said extremitysupports are driven or resisted by a motor controlled by a controller,the device further including a functional electrical stimulationcontroller, wherein the functional stimulation controller and the firstand second extremity supports and cycling base are configured to assista subject in moving his or her upper or lower extremities; said devicefurther including an automatic spasm control system comprising a monitorconfigured to continuously monitor a torque required to rotate one orboth of said left and right extremity supports, said controllerconfigured to calculate a rate of change of said torque, a maximumservo-motor speed and a maximum servo-motor ramp-up rate, saidfunctional electrical stimulation controller configured to calculate amaximum electrical stimulation, a maximum stimulation ramp-up rate.

According to further embodiments of the invention the controller managesisometric functional electrical stimulation to the subject's muscles.

According to further embodiments of the invention there is provided amethod of exercising a subject's extremities comprising: placing thesubject's extremities in an extremity support of a device describedherein, placing electrical stimulation electrodes on the subject'sextremities, and exercising the subject's extremities.

According to further embodiments of the invention, the exercising stepincludes actively assisting the subject in moving the subject'sextremities by rotating the extremity supports around an extremitysupport pivot point.

According to further embodiments of the invention, the method includesassisting the subject to exercise the subject's extremities throughisometric functional electrical stimulation.

According to further embodiments of the invention, the method includesincreasing muscle electrical stimulation and reducing motor assistance.

According to further embodiments of the invention, electricalstimulation evokes coordinated muscle contractions and the extremitysupports' do not drive rotation.

According to further embodiments of the invention, the method includesincreasing motor assistance and decreasing electrical stimulation.

According to further embodiments of the invention, the automatic spasmcontroller is configured to identify a possible onset of spasm when amonitored amount of torque or rate of change of torque exceeds apredetermined value, and when a monitored amount of torque or rate ofchange of torque exceeds said predetermined value, and to compare acurrent crank speed to said calculated maximum crank speed and saidelectrical stimulation controller configured to compare a current levelof electrical stimulation to said calculated maximum stimulation.

DESCRIPTION OF THE DRAWINGS

The subsequent description of the preferred embodiments of the presentinvention refers to the attached drawings, wherein:

FIG. 1 shows an RT300™ Functional Electrical Stimulation cycling systemby Restorative Therapies, with an automatic spasm control system of theinvention installed in the RT300™'s controller.

DETAILED DESCRIPTION OF THE INVENTION

The invention summarized above may be better understood by referring tothe following description, the accompanying drawings, and the claimslisted below. This description of an embodiment, set out below to enableone to practice an implementation of the invention, is not intended tolimit the preferred embodiment, but to serve as a particular examplethereof. Those skilled in the art should appreciate that they mayreadily use the conception and specific embodiments disclosed as a basisfor modifying or designing other methods and systems for carrying outthe same purposes of the present invention. Those skilled in the artshould also realize that such equivalent assemblies do not depart fromthe spirit and scope of the invention in its broadest form. While theinvention is described herein in the context of an RT300-SLSA cyclingsystem, it may be used in conjunction with any FES system, including thesystems described in U.S. Pat. Nos. 8,905,951 and 9,511,256, thedisclosures of which are incorporated herein in their entirety.

As shown in FIG. 1, one embodiment of the present invention comprises atherapeutic muscle exercise device 100 used to treat patients who mayhave partial or entire paralysis of the arms and/or legs. The device 100comprises a cycling base 105 that is mounted on a mobile support 103.

The cycling base 105 has a first extremity support 108 and a secondextremity support 109. It is contemplated that in some embodiments asingle extremity support may be included to facilitate treatment ofsubjects who have lost a limb. Each extremity support 108 and 109 areattached to the cycling base by a first rotating arm 114 and a secondrotating arm 115, respectively.

The rotating arms 114 and 115 attach to the extremity supports 108 and109 at a extremity support pivot point 130 and 131. The configurationallows the foot of the subject to rotate as normally as it would whenperforming a cycling motion naturally. The rotating arms connect to thecycling base 105 at a base pivot point 140. In a preferred embodiment,the base pivot point 140 comprises a shaft that passes through a channelthat extends through the base; the shaft connects the base end of thefirst rotating arm 114 to the base end of the second rotating arm 115.In such embodiment, the shaft then rotates uniformly around the basepivot point 140. In other embodiments, the rotating arms 114, 115 mayconnect to two independently rotatable shafts at the base pivot point140 allowing the extremity supports 108 and 109 to rotate independentlyof one-another.

The cycling base 105 also includes two calf supports 148, 149. In someembodiments, the calf supports 148 and 149 are connected to theextremity supports 108 and 109 though an attachment link 153, 154. Inother embodiments, the calf supports 148 and 149 may not be linked tothe extremity supports 108 and 109.

The device 100 also includes a functional electrical stimulationcontroller 175. The controller 175 manages the electrical impulsesprovided to the subject's muscles through a series of leads 159, whichare connected to the controller 175 through a lead cable 156. Thecontroller 175 also controls a motor (not shown) that controls the speedof rotation of the rotating arms 114 and 115. The controller 175coordinates the rotation of the rotating arms 114 and 115 in conjunctionwith functional electrical stimulation through the leads 159 dependingon the level of need of the subject. In some instances, the controller175 will direct full movement of the rotating arms 114 and 115 inconjunction with electrical stimulation resulting in fully FES evokedmovement. In the alternative, the controller 175 may reduce the level ofassistance provided by the motor and the electrical stimulation allowingvolitional movement by the subject. In yet a further embodiment, thecontroller 175 will not provide any assistance in order to allow thesubject to rotate the extremity supports 108, 109 without assistance.The controller 175 provides such assistance as needed by the subject anddirected by the user.

Likewise, wrist and hand supports 208 and 209 may be provided andconfigured to attach to rotating arms 214 and 215 at base pivot point240, and subsequent attachment to wrist and hand supports 208 and 209.

In one embodiment, a method for exercising a subject's extremities isprovided. According to this embodiment, the system continuously rotatesat the set speed and it either assists or resists the patient's efforts.The patient's efforts are either volitional or evoked by FES. In a firststep of the method the system's motor moves the subject's extremitiesand the controller provides initial muscle electrical stimulation. Thisfirst step can be referred to as a warm up step. In a subsequent step,referred to as active transition, the controller increases muscleelectrical stimulation and reduces motor assistance until the muscletakes over movement of the extremity supports or 100% stimulationthreshold is reached. In a subsequent step, referred to as the activestep, electrical stimulation evokes coordinated muscle contractions asthe rotating arms 114 and 115 (and/or 214 and 215) turn around the pivotpoint 140 (and/or 240) resulting in the subject's muscles performing thecycling motion. The combination of the rotating arms 114 and 115 (and/or214 and 215) connected at the pivot point 140 (and/or 240) is alsoreferred to herein as the crank. Once muscle fatigue is reached and/ordetected by the controller, electrical stimulation is reduced and themotor of the cycling base takes over for cycling motion. In a finalstep, referred to as cool down, the motor completely takes over cyclingmotion allowing subject's muscles to rest while permitting movementthrough the range of motion.

According to a further embodiment, an automatic spasm control feature ofthe present invention monitors the amount of torque required to move thepatient's arms or legs from the beginning of the therapy session. Thesystem also monitors the pattern and rate of change, or smoothness, ofthe required torque through each rotation of the ergometer crank. Theautomatic spasm control system of the invention uses increases inrequired torque as well as decreases in the smoothness of the requiredtorque to detect muscle tone and to detect if a muscle spasm isoccurring.

For each amount of muscle tone detected, the automatic spasm controlsystem of the invention sets a maximum stimulation level, a maximumstimulation ramp-up rate, a maximum crank speed, and a crank ramp-uprate. If a full muscle spasm occurs, then the automatic spasm controlsystem inhibits the motor from rotating the crank for a period of time,and then tries to start the therapy session again.

The following example follows a patient starting a leg therapy sessionand the stimulation level is increasing. If the patient experiences theonset of a spasm, the torque required to assist leg rotation will beginto fluctuate which fluctuation in torque will be detected by theautomatic spasm control system. Similarly, if the patient starts toexhibit high muscle tone, the motor torque required to assist the legcrank rotation will increase and the automatic spasm control system willdetect this increase. In either event, automatic spasm control systemwill calculate the maximum stimulation level and cycling cadenceappropriate to prevent the muscle tone from increasing or developinginto a muscle spasm.

If the current therapy is stimulating at a higher level than thecalculated maximum stimulation level appropriate to prevent the muscletone from increasing or developing into a spasm, the automatic spasmcontrol system will cause the stimulation level to be decreasedaccordingly. Likewise, if the current leg therapy cadence is currentlygoing faster than the maximum cycling cadence to prevent the muscle tonefrom increasing or developing into a spasm, the automatic spasm controlsystem will cause the cadence rate to be reduced.

Conversely, if the current stimulation level is lower than thecalculated maximum stimulation value, then the system will calculate themaximum stimulation level ramp up rate that is appropriate to preventthe muscle tone from increasing or a muscle spasm from developing. Thesystem will allow the stimulation level to increase at a rate no greaterthan this maximum.

If the cadence is lower than the calculated maximum cycling cadencevalue, then the system will calculate the maximum speed ramp up ratethat is appropriate to prevent the muscle tone from increasing or amuscle spasm from occurring. The system will allow the cadence toincrease at a rate no greater than this calculated maximum rate.

If the muscle tone continues to increase, then all of these maximumlevels will be further reduced. This acts to allow the patient's musclesto accommodate the stimulation so that eventually the muscle tone willreduce. As the muscle tone reduces, the system will increase all thesemaximum levels. Once there is no or minimal muscle tone, no limits areimposed by the system. At this point the FES therapy session willcontinue using its preset stimulation level and cadence parameters.

In the event that the detected muscle tone does not decrease over time,indicating that the muscles are either not accommodating the prescribedcadence or stimulation levels, the automatic spasm control system willslowly allow a higher cadence and stimulation level. This allows apatient to progress to active cycling even though he/she is exhibitingtone. In this case it is likely that the detected tone was caused not byspasm, but by another factor such as myotatic reflex. According tovarious different embodiments of the invention, the system may makeadjustments to cadence and stimulation levels appropriately for spasmand myotatic reflex.

The invention has been described with references to a preferredembodiment. While specific values, relationships, materials and stepshave been set forth for purposes of describing concepts of theinvention, it will be appreciated by persons skilled in the art thatnumerous variations and/or modifications may be made to the invention asshown in the specific embodiments without departing from the spirit orscope of the basic concepts and operating principles of the invention asbroadly described. It should be recognized that, in the light of theabove teachings, those skilled in the art can modify those specificswithout departing from the invention taught herein. Having now fully setforth the preferred embodiments and certain modifications of the conceptunderlying the present invention, various other embodiments as well ascertain variations and modifications of the embodiments herein shown anddescribed will obviously occur to those skilled in the art upon becomingfamiliar with such underlying concept. It is intended to include allsuch modifications, alternatives and other embodiments insofar as theycome within the scope of the appended claims or equivalents thereof. Itshould be understood, therefore, that the invention may be practicedotherwise than as specifically set forth herein. Consequently, thepresent embodiments are to be considered in all respects as illustrativeand not restrictive.

1. A functional electrical stimulation device comprising: a leftextremity support and a right extremity support, wherein both extremitysupports are connected to a primary drive motor that causes theextremity supports to move in a reciprocal motion; said left extremitysupport further connected to a left extremity support servo motor andsaid right extremity support connected to a right extremity supportservo motor, wherein each of said right and left extremity support servomotors causes its respective extremity support to rotate about an axis;a control unit connected to the left and right extremity support servomotors and which controls the actuation of the left and right extremitysupport servo motors, wherein the control unit further comprisesfunctional electrical stimulation leads attached to skin adhesiveelectrodes and wherein said adhesive electrodes deliver electricalstimulation to a patient's muscles, said device further comprising anautomatic spasm control system comprising a monitor configured tocontinuously monitor a torque required to rotate one or both of saidleft and right extremity supports and a controller configured tocalculate a rate of change of said torque, and to calculate a maximumelectrical stimulation, a maximum stimulation ramp-up rate, a maximumservo-motor speed and a maximum servo-motor ramp-up rate.
 2. Thefunctional electrical stimulation system recited in claim 1, furthercomprising two drive arms connecting said primary drive motor to each ofsaid left and right extremity supports, wherein said drive arms comprisevarious attachment points for connecting to corresponding right and leftcranks at different attachment positions.
 3. The functional electricalstimulation system recited in claim 2, wherein the extremity supportsare attached to the drive arms by the corresponding left and rightcranks.
 4. The functional electrical stimulation system of claim 1, saidcontroller of said automatic spasm control system further configured toidentify a possible onset of spasm when a monitored amount of torque orrate of change of torque exceeds a predetermined value, and when amonitored amount of torque or rate of change of torque exceeds saidpredetermined value, to compare a current level of electricalstimulation to said calculated maximum stimulation and to compare acurrent crank speed to said calculated maximum crank speed and to sendinstructions to said control unit connected to the left and rightextremity support servo motors and to said functional electricalstimulation leads to reduce the amount of electrical stimulation andcrank speed.
 5. A therapeutic muscle exercise device, comprising: acycling base configured to accept a subject's upper or lower extremitiesand assist a subject in exercising the subject's muscles; the cyclingbase comprising a first extremity support and a second extremitysupport, wherein said extremity supports are driven or resisted by amotor controlled by a controller, the device further comprising afunctional electrical stimulation controller, wherein the functionalstimulation controller and the first and second extremity supports andcycling base are configured to assist a subject in moving his or herupper or lower extremities; said device further comprising an automaticspasm control system comprising a monitor configured to continuouslymonitor a torque required to rotate one or both of said left and rightextremity supports, said controller configured to calculate a rate ofchange of said torque, a maximum servo-motor speed and a maximumservo-motor ramp-up rate, said functional electrical stimulationcontroller configured to calculate a maximum electrical stimulation, amaximum stimulation ramp-up rate.
 6. The device of claim 1, wherein thecontroller manages isometric functional electrical stimulation to thesubject's muscles.
 7. A method of exercising a subject's extremitiescomprising: placing the subject's extremities in an extremity support ofa device of claim 5; placing on the subject's extremities, andexercising the subject's extremities.
 8. The method of claim 7, whereinsaid exercising step comprises actively assisting the subject in movingthe subject's extremities by rotating the extremity supports around anextremity support pivot point.
 9. The method of claim 8, furthercomprising assisting the subject to exercise the subject's extremitiesthrough isometric functional electrical stimulation.
 10. The method ofclaim 9, further comprising increasing muscle electrical stimulation andreducing motor assistance.
 11. The method of claim 10, whereinelectrical stimulation evokes coordinated muscle contractions and theextremity supports' do not drive rotation.
 12. The method of claim 11,further comprising increasing motor assistance and decreasing electricalstimulation.
 13. The device of claim 5, said controller furtherconfigured to identify a possible onset of spasm when a monitored amountof torque or rate of change of torque exceeds a predetermined value, andwhen a monitored amount of torque or rate of change of torque exceedssaid predetermined value, and to compare a current crank speed to saidcalculated maximum crank speed and said electrical stimulationcontroller configured to compare a current level of electricalstimulation to said calculated maximum stimulation.